Metal and metal-alloy stocks are ground primarily in order to disclose the possible presence of surface cracks or fissures and slag/inclusions, so that the stock can be worked locally and brought to a satisfactory state prior to being rolled. The stock or billet is thus ground to remove a surface layer which contains slag and like impurities which rise to the surface as the stock is cast. When cold stock is ground, the stock will invariably be coated with a heavy oxide-containing layer that forms as the stock cools. This layer therefore has to be removed together with the aforesaid slag inclusions.
When working or machining in accordance with known methods stock which is, e.g. to be subsequently rolled in a rolling mill, coarse grinding disks are often used and the stock is ground in strip-like patterns along a plurality of narrow, mutually parallel channels, which results in low grinding capacity. Furthermore, this grinding procedure leaves a rough and rippled surface, and the stock cannot be ground until the temperature thereof has fallen to a level at which the grinding disk will not explode. Because of the relatively long time taken to complete this grinding procedure, the stock will cool to a still lower temperature. Consequently, during this cooling period there is formed a relatively thick layer of oxides and scale, which cannot be machined readily and which can only be ground away with great difficulty and with high energy inputs. It is also necessary to grind through the layer, therewith removing excessive quantities of valuable underlying material.
Furthermore, the abrasive tool used is subjected to pronounced wear, which further impairs the economy of conventional methods which use grinding disks, grinding rolls or like abrasive tools.
One example of the presently known techniques is found in DE-OS 3 600 144 published on the 9th July 1987. This publication describes a method for the removal of scale with the aid of two mutually opposing grinding rolls. This publication reveals that those skilled in this art consider grinding with an abrasive belt to give a poor grinding result, due to the difficulty of applying the high grinding pressure required to remove the scale and the oxide layer formed on the rolled stock as it cools.
The known methods are thus encumbered with a large number of drawbacks. These drawbacks are avoided by the present invention, which relates to a method for grinding metal or metal-alloy stock, billets and like workpieces in a hot state, by means of grinding with an abrasive belt in accordance with the disclosure which follows.